Drive through car washes are frequently provided with rotatable elongated cylindrical wheels or brushes for cleaning the front, sides and rear portions of the vehicle exterior. In order to wash the front and rear portion of the vehicle, rotatable wheels are frequently positioned on the distal ends of elongated arms which extend over the path of the vehicle. Upon engagement with the vehicle, the wheels must quickly move onward toward the vehicle sides in order to allow the vehicle to advance. Once the sides of the vehicle are washed, the wheels move inward to wash the rear of the vehicle as it is moving longitudinally away from the rotating wheel station. In order to effectively wash the front and rear of the vehicle, it is necessary to allow the wheel to generally move transversely so the wheel can effectively follow the contour of the vehicle.
When washing the front of the vehicle, if the wheel does not effectively move out of the vehicle path, the car wash mechanism can be damaged. If the wheel does not effectively move inboard after the side of the vehicle is washed, the rear of the vehicle will not be cleaned properly. It is therefore necessary to mount the wheel in a manner in which it is capable of limited longitudinal movement along the path of the vehicle.
There are two distinctly different design approaches to solve this longitudinal wheel movement problem. One approach is to mount the rotatable wheel assembly on a sliding carriage which translates the length of a pivotal arm and extends over the path of the vehicle. Car wash apparatus of this type is illustrated in U.S. Pat. No. 4,424,602, Belanger et al. and is incorporated by reference in its entirety. An alternative design suspends the wheel assembly from the end of a pivotal arm at a fixed location. The wheel assembly is allowed to deflect relative to the arm in response to engagement with the vehicle. Deflection is achieved by either using a flexible wheel shaft such as a plastic shaft or mounting the wheel and motor assembly on a flexible elastic doughnut-like coupling. The coupling is loaded in tension and located between the motor and the shaft. Alternatively, a universal coupling can be placed between the drive motor and wheel.